The biggest haul was made at a mosque complex in the east of the city.

Soldiers also found a house which contained a laboratory and instructions on how to make anthrax and blood agents, an Iraqi official said.

But US marines say it may be several weeks before civilians who fled the city can return. Following the US-led offensive, the city remains without power or water.

The discoveries came as hundreds of British troops from the Black Watch took part in a fresh offensive against suspected Saddam Hussein loyalists living on the bank of the Euphrates river in central Iraq.

In other developments:

Two car bombs explode in Samarra. The first injures at least 10 people. The second claims no victims except the suicide bomber, police say.

US officials say they found five new bodies, including the corpses of some Iraqi soldiers, in the northern city of Mosul - the scene of a recent upsurge in attacks

Police in southern Iraq arrest five suspected foreign fighters - two Saudis, two Tunisians and one Libyan - they claim were planning to mount attacks in Basra.

'Foreign fighters' centre'

Marine commanders said troops moving from house to house had discovered large numbers of weapons stores, including stocks of up to 700 mortar shells.

Kalashnikov rifles, ammunition, rocket-propelled grenades and heavy cannon have also been found throughout the city, officers said.

Weapons caches, many in the south of Falluja - the last area taken by the marines - were often marked by a brick suspended on a piece of string outside a house, they added.

Aid organisations need to assess how many need help in Falluja

"The amount of weapons was in no way just to protect a city," said Maj Jim West, a Marine intelligence officer.

"There was enough to mount an insurgency across the country," he added.

Earlier, Iraqi Minister of State Kassim Daoud told a news conference: "Soldiers from the Iraqi National Guard found a chemical laboratory that was used to prepare deadly explosives and poisons.

"They also found in the lab booklets and instructions on how to make bombs and poisons. They even talked about the production of anthrax."

But there has been no confirmation of this from US troops.

The marines have said they found a laboratory in the past week, but that it was manufacturing explosives, not chemical weapons.

'Hotbed'

The US has claimed Falluja was a centre for foreign fighters who had come to Iraq to fight the coalition.

Earlier this week Iraq's interim defence minister said 60 Arab fighters were among those arrested in Falluja.

The Americans claim to have killed at least 1,000 Iraqis in the Falluja assault launched two and a half weeks ago.

More than 50 marines died and more than 400 were wounded.

The number of Iraqi civilians killed and injured when they were caught up in the fighting is still not known.

The Iraqi Red Crescent said on Thursday it had managed to deliver food aid, and that its volunteers would stay to help bury the dead and evacuate families still trapped in Falluja.